Differential pressure sensors, control, and associated methods

Abstract

Differential pressure sensors, control, and associated methods are disclosed. An example apparatus includes a piston including a first cylindrical section having a first diameter and first and second annular surfaces, each of the first and second annular surfaces having a first surface area, and second cylindrical sections having a second diameter less than the first diameter, the first cylindrical section between the second cylindrical sections, and a housing including a first chamber to receive a first fluid, the first fluid to apply a first pressure on the first annular surface, a second chamber to receive a second fluid, the second fluid to apply a second pressure on the second annular surface, and a third chamber including a third fluid, the third annular surface to apply a third pressure on the third fluid, the third pressure corresponding to a difference between the first pressure and the second pressure.

What is claimed is: 
     
         1 . An apparatus to measure differential pressure, the apparatus comprising:
 a piston including:
 a first cylindrical section having a first diameter and first and second annular surfaces, each of the first and second annular surfaces having a first surface area; and 
 second cylindrical sections having a second diameter less than the first diameter, the first cylindrical section between the second cylindrical sections, one of the second cylindrical sections including a third annular surface having a second surface area, the second surface area substantially equal to the first surface area; and 
   a housing including:
 a first chamber to receive a first fluid, the first fluid to apply a first pressure on the first annular surface; 
 a second chamber to receive a second fluid, the second fluid to apply a second pressure on the second annular surface; and 
 a third chamber including a third fluid, the third annular surface to apply a third pressure on the third fluid, the third pressure corresponding to a difference between the first pressure and the second pressure. 
   
     
     
         2 . The apparatus of  claim 1 , further including a pneumatic valve operatively coupled to the third chamber, the pneumatic valve to move to a first position when the third pressure is at or above a threshold, the pneumatic valve to move to a second position when the third pressure is below the threshold. 
     
     
         3 . The apparatus of  claim 2 , wherein the pneumatic valve is operatively coupled to an air supply and to one or more control valves, the pneumatic valve to enable flow of air from the air supply to the one or more control valves when the pneumatic valve is in the first position, the pneumatic valve to restrict the flow of air from the air supply to the one or more control valves when the pneumatic valve is in the second position. 
     
     
         4 . The apparatus of  claim 1 , wherein the housing includes a first housing coupled to a second housing, the first chamber is defined in the first housing, the second and third chambers defined in the second housing. 
     
     
         5 . The apparatus of  claim 4 , further including a bleed screw operatively coupled to the second housing. 
     
     
         6 . The apparatus of  claim 1 , wherein the third fluid includes glycol. 
     
     
         7 . The apparatus of  claim 1 , wherein the first fluid is from a fluid inlet of a first compressor, and the second fluid is from a fluid outlet of a second compressor, the second compressor fluidly coupled to the first compressor. 
     
     
         8 . The apparatus of  claim 1 , further including:
 a groove extending along a circumference of the first cylindrical section; and   a seal positioned in the groove, the seal to restrict fluid flow between the first chamber and the second chamber.   
     
     
         9 . A method to measure differential pressure, the method comprising:
 providing a first fluid to a first chamber of a housing, the first fluid to apply a first pressure on a first annular surface of a first cylindrical section coupled between second cylindrical sections to define a piston, the first cylindrical section having a first diameter and a second annular surface, the first annular surface and the second annular surface on opposite ends of the first cylindrical section, each of the first and second annular surfaces having a first surface area, the second cylindrical sections having a second diameter less than the first diameter, one of the second cylindrical sections including a third annular surface having a second surface area, the second surface area substantially equal to the first surface area;   providing a second fluid to a second chamber of the housing, the second fluid to apply a second pressure on the second annular surface; and   providing a third fluid to a third chamber of the housing, the third annular surface to apply a third pressure on the third fluid, the third pressure corresponding to a difference between the first pressure and the second pressure.   
     
     
         10 . The method of  claim 9 , further including operatively coupling a pneumatic valve to the third chamber, the pneumatic valve to move to a first position when the third pressure is at or above a threshold, the pneumatic valve to move to a second position when the third pressure is below the threshold. 
     
     
         11 . The method of  claim 10 , further including operatively coupling the pneumatic valve to an air supply and to one or more control valves, the pneumatic valve to enable flow of air from the air supply to the one or more control valves when the pneumatic valve is in the first position, the pneumatic valve to restrict the flow of air from the air supply to the one or more control valves when the pneumatic valve is in the second position. 
     
     
         12 . The method of  claim 9 , wherein providing the first fluid to the first chamber of the housing includes providing the first fluid to a first housing coupled to a second housing to define the housing, the first chamber defined in the first housing, the second and third chambers defined in the second housing. 
     
     
         13 . The method of  claim 9 , wherein providing the third fluid to the third chamber includes providing glycol to the third chamber. 
     
     
         14 . The method of  claim 9 , further including providing the first fluid from a fluid inlet of a first compressor and providing the second fluid from a fluid outlet of a second compressor, the second compressor fluidly coupled to the first compressor. 
     
     
         15 . The method of  claim 9 , wherein the first cylindrical section further includes:
 a groove extending along a circumference of the first cylindrical section; and   a seal in the groove, the seal to restrict fluid flow between the first chamber and the second chamber.   
     
     
         16 . An apparatus to measure differential pressure, the apparatus comprising:
 a first cylindrical section having a first diameter and first and second annular surfaces, each of the first and second annular surfaces having a first surface area, a first pressure to be applied on the first annular surface, a second pressure to be applied on the second annular surface; and   second cylindrical sections having a second diameter less than the first diameter, the first cylindrical section between the second cylindrical sections, one of the second cylindrical sections including a third annular surface having a second surface area, the second surface area substantially equal to the first surface area, the third annular surface to apply a third pressure corresponding to a difference between the first pressure and the second pressure.   
     
     
         17 . The apparatus of  claim 16 , further including:
 a groove extending along a circumference of the first cylindrical section; and   a seal positioned in and extending along the groove.   
     
     
         18 . The apparatus of  claim 17 , wherein the groove is a first groove, the circumference is a first circumference, the seal is a first seal, and further including:
 a second groove extending along a second circumference of the one of the second cylindrical sections; and   a second seal positioned in and extending along the second groove.   
     
     
         19 . The apparatus of  claim 16 , further including an aperture extending into the one of the second cylindrical sections from the third annular surface. 
     
     
         20 . The apparatus of  claim 16 , wherein the third pressure is between 500 pounds per square inch (psi) and 3000 psi.